In many applications, it is necessary that parts having various configurations and dimensions be heat treated to improve their material characteristics. In a normal heat treatment process, a part is heated to a high temperature, is held there for a period of time and thereafter is quenched, for example in an oil bath, to reduce its temperature quickly. In order to retain a plurality of parts, such that they can be properly heat treated, it has been standard practice to enclose the parts in a four-sided basket which rests upon a heat treating tray. The heat treating tray is placed on a conveyor system so that the parts can be easily moved into and out of the furnace and the quenching bath. Due to both the high temperature of the heat treatment process and the large temperature fluctuation which occur within a very short period of time, there is a tendency for thermal stresses to develop in the baskets. These thermal stresses can cause the basket sides to warp and crack after a period of time thereby making them unusable. Various attempts to alleviate this problem are described in U.S. Pat. Nos. 2,145,258; 2,430,521; 2,453,511; 2,621,912 and 3,498,597. These patents teach the use of flexible members which are used to make up the basket sides or the use of reinforcing members to make the sides more rigid. Despite these efforts, there is still a need to provide a heat treating basket which exhibits a longer useful life and is less susceptible to being warped and cracked during repeated use in the heat treating process.
Now an improved basket for retaining parts during heat treatment has been invented which solves the above mentioned problem.